The toxic gases released by industries and other sources have a significant impact on humans and other life on the earth. Exposure to these gases at higher concentration may cause severe health issues and may even lead to death. Thus, the rapid detection of hazardous gases in the environment with high sensitivity is crucial to save the lives. However, the low sensitivity of the existing sensors limits their usage in detecting toxic gases in the air. To address this, we report a highly sensitive Hydrogen Sulfide (H₂S) gas sensor based on 2D Zinc Oxide (ZnO) nanostructures. H₂S is a poisonous and flammable gas and as per American Conference of Government Industrial Hygienists, the acceptable limit of H₂S in the air is 10 ppm. When the concentration exceeds 10 ppm, the human nose loses the ability to detect H₂S, which causes disastrous effects. The proposed sensor was tested in the range of 0.5-4 ppm H₂S and it exhibited a response of 750% upon exposure of 4 ppm H₂S. The response and recovery times are < 250 seconds and <430 seconds respectively in the tested range of concentrations of target gas.